Shadow mask mounting brackets moving mask toward screen with radial mask expansion



1970 r J. w. SCHWARTZ ETAL 3,524,971 SHADOW MASK MOUNTING BRACKETSMOVING MASK TOWARD SCREEN WITH RADIAL MASK EXPANSION INVEJVTORS: JAMESW. SCHWARTZ LASLO J. JAVORIK Filed Jan. 11, 1967 d ATT'YS 3,524,971 ficePatented Aug. 18, 1970 U.S. Cl. 313-85 2 Claims ABSTRACT OF THEDISCLOSURE A color television tube mask mounting adapted tosubstantially compensate for the mechanical shift of the mask openingsduring operation. The mask mounting is constructed to move the maskaxially so as to maintain register of the mask openings with theelectron paths which extend from the guns to the phosphor dots.

SUMMARY OF INVENTION The inventive mask mounting includes a uniquecoupling for interconnecting a post or like rigid piece on the envelopeof the television tube with the shadow mask. The coupling is responsiveto the change in size of the shadow mask so as to move the same in adirection parallel to the axis of the tube.

The invention is explained in conjunction with the accompanying drawingin which- FIG. 1 is a fragmentary elevational View of the faceplateportion of a rectangular color television tube, with the above-mentionedmask mounted in place;

FIG. 2 is a fragmentary cross-sectional view such as would be seen alongthe sight line 2-2 applied to FIG. 1, the showing in FIG. 2 being onenlarged scale, relative to FIG. 1;

FIG. 3 is a schematic representation of the movement of a particularshadow mask opening according to the prior art and according to theinventive teaching;

FIG. 4 is a fragmentary sectional view on an enlarged scale of theencircled portion in FIG. 1;

FIG. 5 is a fragmentary view of a portion of FIG. 4 but with the partsthereof in a different operative condition; 7

FIG. 6 is a sectional view taken along the line 6-6 of FIG. 4;

FIG. 7 is a fragmentary sectional view of a modified form of theinvention; and

FIG. 8 is a sectional view taken along the line 8-8 of FIG. 7.

In the illustration given, the numeral 10 designates generally the faceplate of a rectangular color television tube. The view in FIG. 1 islooking forwardly from the interior so as to see the face plate lipthisconstituting the portion ultimately fused to the funnel portion of thetube to provide the overall glass envelope of the tube. The inside ofthe face plate is equipped with the usual phosphor dot screen as at 10b(see FIG. 2) and mounted inwardly of the screen is a shadow maskgenerally designated 11, conventionally employed with a screen havingtriads of dots in green, red and blue. The shadow mask 11 includes aperimetric frame about a perforated, curved face. It is the means forsupporting this mask with which the instant invention is concerned. Forthis purpose, I depart from the usual posts and spring clips and employinstead, connection means which are responsive t the change in mask size(i.e., dimension) to move the mask axially to compensate for the sizechange.

OPERATION GENERALLY Reference is made now to FIG. 2 wherein the shadowmask 11 is seen in relatively heavy line and in the position when thetube is not in operation or under any kind of stress tending to changethe size of the shadow mask 11. In the condition of the mask designated11 in FIG. 2, it will be seen that an electron beam 12 passes through agiven opening 13 in the mask 11. As the mask changes in sizeusually dueto thermal expansion, the mask normally tends to expand laterally so asto position the opening 13 laterally outwardly of its original position.This is seen in FIG. 2 at 13 but relative to a chain line showing of themask as at 11. It will be appreciated that with the ordinaryinstallation, the mask 11 is not permitted to move axially so that themovement of the opening 13 is substantially only laterally, therelatively lighter chain line showing of the mask designated 11' in FIG.2 not corresponding to actual operation but being exaggerated in orderto more graphically illustrate the operation of the invention.

According to the invention, however, the movement of the opening 13under stress is not merely just laterally as designated by the position13 but is additionally axial, i.e., to the position designated 13relative to mask position 11" in FIG. 2. As seen in FIG. 3, the positionof the opening designated 13" is along the line of the beam 12. Thisdirection is designated 14 in contrast to the direction 15 of ordinarymovement in an uncompensated mask. This means therefore, that a beamwill necessarily fall on its intended dot as at 16 in FIG. 2. ratherthan on an unintended dot or different portion of the screen as at 16'.

It will be appreciated that the absolute movements involved are rathersmall-of the order of .00 to .00 "but these are significant when it isconsidered that the mask openings are correspondingly small-300,000openings 13 being provided in a shadow mask for a 23- inch tube.

By moving the mask axially of the tube 10 toward the screen 1012, Icompensate for misregister of the openings 13 in a unique manner. Thecompensation is essentially a dilferential compensation-hence a truecompensation. In the case where the mask 11 and the face plate 10 expandidentically, there will be no axial movement since none is required.However, the usual case finds the metal mask (i.e., cold-rolled steel)expanding more than the glass face plate. The source of heat for theexpansion is the electron beam 12 which first impinges on the mask (11,normally causing it to increase in temperature 30 C. or so. The tube 10itself may increase in temperature only 10 C. or so. Alternatively, itwill be appreciated that any change in size of the mask will result inthe displacement when the size change is relative to the envelope andthis may occur, for example, because of a pressure differential as wellas because of a temperature differential.

According to the invention, there is provided a mask mounting which isresponsive to size or geometric factors and which is independent oftemperature. Although other devices have been advanced for remedying theproblem to which this invention is directed, these devices have beentemperature-dependent, i.e., involving the use of bimetals or the like.This has stemmed from the fact that those in the art have focused uponone of the significant factors which develop undesirable misregister.However, in compensating for temperature rise, they have been dealingwith what might be considered a secondary phenomenon, as contrasted tothe primary phenomenon the misregister due to change in size itself.There are instances where the ambient temperature has risen so that boththe temperature of the glass envelope and the frame increase together.In such a case, providing a mounting device to shift the mask upon justits increase 'in tempera ture leads to an improper compensation. Toprovide the movement of the mask, I employ a mask-envelope connection asseen in FIG. 4, as described below.

MOUNTING CONSTRUCTIQN Referring now to FIG. 4, it will be seen that theenvelope 10 carries a mounting post 17, a plurality of the posts 17being provided as can be appreciated from a consideration of FIG. 1. Themounting post 17 projects inwardly of the envelope 1!) and is engaged bya fitting generally designated 18 which in turn is rigidly secured (asby welding) to the mask 11. The fitting 18 includes a spring portion 19which engages a projection 20 provided on the post 17. The projection20, in the portion thereof engaged by the spring portion 19, is V-shapedas can be appreciated from a consideration of FIG. 6.

The projection 20 is also equipped with a notch or a recess as at 21which is engaged by a bracket portion 22 provided on the fitting 18. Thebracket portion 22 is relatively flexible, being weldably secured as at23 to the spring portion 19 and equipped with stiffener ribs 24 so as toconfine any deformation to the area designated 25 in FIG. 4. As the mask11 increases in size, the bracket 22 assumes a different angularconfiguration in the portion designated 25" (see FIG. so as to reducethe dimension x, of FIG. 4 to the dimension x in FIG. 5 while increasing the dimension y to that designated y in FIG. 5. This moves themask axially-to the position 11" of FIG. 5. In doing this, the bracket22 has the leg portion equipped with the ribs 24 pivot about the legportion secured as at 23 (see FIG. 4) so as to decrease the angleincluded between these leg portions.

An alternative construction can be seen in FIGS. 7 and 8 wherein thepost is designated 117, being embedded partially in the envelope 110 forthe purpose of moveably supporting the mask 111. Each post has aprojection 120 corresponding to the showing in FIG. 4 for engagement bymeans of a fitting generally designated 118. Again, the fitting 118 isequipped with the spring portion as at 119. The bracket portion 122,instead of engaging a notch as in FIG. 4 is seen to bear upon aninclined plane portion 121. For this purpose, the bracket portion 122may be equipped with a beveled contacting edge as seen in FIG. 7.

In the practice of this embodiment of the invention, the mask 111 issnapped into place, making use of the spring clip portion 119 whichengages one side of the post portion 120, the other side 121 of a givenpost 117 being engaged by the laterally-extending projection 122. Upondifferential expansion of the mask 111 relative to the envelope 110, theentire mask moves by virtue of the 4 engagement of the parts 122 and 121so that when the mask expands, the mask slides along the inclined planeto move axially toward the screen of the face plate 10.

While in the foregoing specification I have described the invention indetail, it will be appreciated that many variations may be made in thedetails of the invention without departing from the spirit and scope ofthe invention.

We claim:

1. In a color television tube having :a faceplate panel with an array ofphosphor dots to provide an image screen and an apertured shadow maskadjacent said screen for admitting the passage of electron beams for theselective excitation of said dots, an improved mounting system formounting said mask to said tube for shifting the mask toward said screenaxially of said tube when said mask is heated as a function of thedifferential expansion of said mask relative to said faceplate panelcomprising a plurality of posts projecting inwardly of said tube forreceiving said mask, each post defining a projection having a transverseV-shaped surface facing away from said screen and a limiting surfacefacing said screen, and a plurality of fittings on said shadow mask, onefor each of said posts, and including a hook-shaped spring memberextending outwardly and rearwardly of said mask and defining a. groovefor engaging said V-shaped surface of an associated post thereby to biassaid mask in a rearward position relative to said screen, and adeformable bracket member having a first portion secured to said maskand a second portion angularly inclined at a bend line relative to saidfirst portion and having a distal edge received in the limiting grooveof said associated post whereby when said mask expands due to heatingsaid deformable bracket will bend about said line to shift said maskforward and into registration and said mask upon cooling will revert toits original position under action of said spring member.

2. The mounting system of claim 1 wherein each of said second portionsof said deformable bracket members is ribbed to provide a stiffeningthereof to prevent deformation of said second portion during heating.

References Cited UNITED STATES PATENTS 2,727,172 12/1955 Mark ct a1.2,795,718 6/1957 Van Hekken et al. 2,795,719 6/ 1957 Morrell. 3,370,1942/ 1968 Schwart et a1.

ROBERT SEGAL, Primary Examiner US. Cl. X.R. 3 13-286, 292

